Turnstile antenna



June 23, 1953 N. w. ARAM 2,643,334

TURNSTILE ANTENNA Filed Oct. 23, 1948 4 Sheets-Sheet 2 SBAYS 6- z5' m .F

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HIS AGENT June 23, 1953 N. w. ARAM 2,643,334

TURNSTILE ANTENNA Filed oct. 25, 1948 4 sneetsfsheet s FIG mi 5| //'/1|q f5@ fx 'd FIG BCL F|G.8b FG 8C N N N w 3o WW Ewgso .E

FIGQQ FIGQb FIGQC @QQ Q NATHAN WARAM JNVENToR.

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HIS AGENT June 23, 1953 N. w. ARAM TURNSTILE ANTENNA 4 Sheets-Sheet 4Filed oct. 23, 194s FIGIO wIlL/: WIQ` a IOOj l|02 FIGII IN VEN TOR.

NATHAN WARAM HIS AGENT Patented June 23, 1953 TURNSTILE ANTENNA NathanW. Aram, Park Ridge, Ill., assig'nor to Zenith Radio Corporation, acorporation of Illinois Application October 23, 1948, Serial No. 56,177

(Cl. Z50-33.53)

12 Claims. 1

This invention relates to antennas and more particularly to antennas ofthe turnstile type. It is a primary object of the invention to provide asimpliiied and improved antenna of this type.

In the following description, it will be convenient to refer from timeto time tospecific groups of radiating elements. In general, in aturnstile antenna, the radiating elements are disposed in a pair ofangularly displaced planes, the elements situated in each plane beingreierred to as a "panel of radiating elements. Similarly, forconvenience of reference, each pair of adjacent crossed elements will betermed a) ubay'n In Patent No. 2,338,564 issued on January 4, 194e, toNathan W. Aram for Turnstile Antenna, and assigned to the same assigneeas the present application, there is disclosed and claimed as apreferred embodiment a turnstile antenna employing folded dipoles asradiating elements, each of such elements being arranged for connectionto individual straight feeder lines disposed about the outer surface ofa supporting mast.

It is a particular object of this invention to provide a simpliedturnstile antenna requiring a minimum number of component parts.

It is an important object of this invention to provide a turnstileantenna having novel radiating elements arranged to reduce the number ofrequisite feeder lines.

It is a more specific object of the invention to provide a simplinedturnstile antenna employing radiating elements adapted to unbalancedfeeding, thereby to reduce the number of requisite feeder lines.

It is a further object of the invention to provide a simplied turnstileantenna having improved power gain characteristics.

Yet another object of the invention is to provide an improved turnstileantenna having improved power gain characteristics by virtue of optimumspacing between adjacent bays of radiating elements.

For a vertical panel of horizontal radiators to have maximum gain in thehorizontal direction, the radiators are preferably excited by in-phasecurrents. If, as in conventional turnstile antennas, the radiatingelements are vertically separated by a half-wavelength and are fed bytransmission lines having a propagation velocity approximately equal tothat of a free-space electromagnetic wave, transposition, as for exampleby means of half-wave phasing loops, is required 2 to insure inl-phaseexcitation of the radiating elements.

Still another object of the invention, therefore, is to provide asimplied turnstile antenna including an array of vertically spacedradiating elements exhibiting maximum gain in a horizontal directionwithout requiring the transposition of feeder lines.

It is a more specic object of the invention to eliminate the requirementfor transposition of feeder lines to a turnstile antenna by utilizingloaded transmission lines to feed the successive radiating elements, thepropagation velocity of such transmission lines bearing substantiallythe same ratio to the free-space propagation velocity as does thephysical spacing between such radiators to a free-space wavelength.

Inorder to obtain an omnidirectional horizontal radiation pattern from aturnstile antenna comprising a plurality of radiating elements arrangedin a pair of angularly displaced panels, it is necessary to providequadrature phasing between the exciting currents of the two panels ofradiating elements. Such quadrature phasing is normally obtained by theuse of quarter wave phasing loops.

It is an important object of this invention to provide a furthersimplified turnstile antenna by eliminating the necessity for suchquarter wave phasing loops.

Still another object of the invention is to provide an improved andsimplified turnstile antenna in which quadrature phasing between panelsis obtained by vertical separation of the radiating elements of eachbay.

The features of this invention which are believed to be novel are setforth with particularity in the appended claims. The invention, togetherwith further objects and advantages thereof, may best be understood,however, by reference to the following description taken in connectionwith the accompanying drawings, in

which like reference numerals indicate like ele-y ments, and in which:

Figure 1 is a schematic representation of a novel radiating elementembodying the present invention.

Figure 2 is a perspective view of an improved turnstile antennaembodying the novel element Figure 4 is a graphical representation ofthe power gain characteristic of an antenna such as that shown in Figure2.

Figure 5 is a cross-sectional view of a feeder line which is suitablefor use with the antenna of Figure 2.

Figure 6 is a sectional detail showing the manner in which the coaxialfeeder line is connected to radiating elements other than the uppermostone.

Figure 7 is a sectional detail showing the manner in which the coaxialfeeder line is connected to the uppermost radiating element.

Figures 8a, 8b, and 8c are schematic representations showing alternativeembodiments.

Figures 9a, 9b, and 9c are graphical representations of the radiationpatterns of the antenna of Figure 2.

Figure 10 is a schematic representation of a further embodiment of thisinvention.

Figure 11 is a schematic representation of still another embodiment ofthe invention.

Figure 12 is a schematic representation of still a further embodiment ofthe invention.

With reference to Figure 1, there is shown a novel radiating element 2Bconstructed in accordance with the present invention, such elementcomprising a pair of conductive members 2! and 22 interconnected by aU-shaped conductive member 23, the length of member 22 being sub-rstantially twice that of 2| and -being substantially a half wavelengthor an odd integral multiple of a half wavelength at the frequency to betransmitted. The second conductive member 22 may be grounded atsubstantially its midpoint, thereby to adapt element for directunbalanced feeding. Radiating element 26 may-be fed by a coaxial feederline 24, the inner conductor 2li of which is connected to the free endof rst member 2| and the shield 2S of which is connected to the midpointof member 22.

Viewed in another way, the novel radiating element 2D comprises aquarter-wave folded dipole arm consisting of members Zi'and 23 and halfof member 22, and a quarter-wave simple dipole arm collinear with andelectrically connected to one leg of the folded dipole arm, such simpledipole'arm comprising the other half of member 22. Element 20 as shownmay also be viewed as an unbalanced folded dipole from which the returnbend of the short-circuited loop has been removed. It is contemplatedthat members 2l, 22, and 23 may be either solid or tubular in construction.

It has been found that a radiating element of this typ-e providessubstantially the same radiation pattern as a simple half-wave radiatoror folded dipole of conventional construction. It is thought that thisdesirable result is accomplished because of parasitic excitation of thesimple dipole arm. In other words, provision of a perpendicular imagingplane or collinear imaging conductor apparently gives rise to seriesresonant radiating current components which, together with theanti-resonantradiating components from the loop comprising member 2 I,member 23, and half 'of member 22, suffice tov set up substantially thesame field as that set up by a conventional folded dipole ofthe sameoverall length. i

Element 2] of Figure 1 is particularly advantageous in that it isinherently unbalanced. Since a coaxial line is also essentiallyunbalanced, element 20 may be designed to' preclude the possibility ofany substantial balance-to-unbalance mismatch without the use of labalanoe-to-unbalance impedance transformer. For this reason, the numberof required coaxial feeder lines and fittings may be substantiallyreduced from the -number required when using a conventional balablygrounded. Since the field strength existing at anygiven receiving pointis proportional to the height of the transmitting antenna, the mast Sispreferably located at the highest available position, as for example atthe top of a skyscraper.

A turnstile antenna may comprise a plurality of bays of half-waveradiating elements supported on mast 30, each bay comprising a pair ofelements disposed at right angles to each other. All of the elements ineach panel, that is, those having one direction (for example, north andsouth in one case, and east and west in the other case) are excited byiii-phase currents. Moreover, the elements of one direction (north andsouth for example), are excited in phase quadrature with respect to theelements of the other direction (east and west for example), With thisquadrature excitation, the radiation pattern is substantiallyomnidirectional. Radiation is concentrated toward the horizontaldirection as a function of the number of bays of radiating elements.

While the antenna of Figure 2 has been shown comprising four bays ofradiating elements, it is.

apparent that any number of bays may be elnployed. Furthermore, whilethe antenna arrangements described have been shown to be orientedl in aAvertical direction, it is to be noted that for certain purposes themast and the antenna as a whole may be tilted from the vertical.

For convenience of reference, the various radiating elements arereferred to in the drawings and in this specification as NZ-SZ, E13-W3,etc., the letter combination of each indicium designating the directionof the radiating element and the numeral denoting its position in theseries of radiators, in its particular panel, referred to the bottom ofthe mast 30. Similarly, it is convenient to refer to the individualportions of the radiating elements as N2, E3, S4, etc. 1t is noted,however, that this nomenclature is for ease oi reference only; since theradiation pattern is substantially omnidirectional, the points of thecompass to which the elements are directed are immaterial, and it isobserved that the entire unit may be considered to be rotated by anydesired amount without any substantial effect on the radiation pattern.

Thus it is noted that, in the embodiment of Figure 2, elements N4-S4 andE4-W4, for example, constitute a bay, and elements N-S, N2--S2, N3--S3,and Nfl-S4, for example, constitute a panel.

In the Figure 2 embodiment of the invention, a single feeder line 3l,the construction of which is to be hereinafter described in detail, isemployed to feed the radiating elements, the usual requirement forhalf-wave and quarter-wave phasing loops being eliminated. To this end,the radiating ,elements constituting each bay (N3-S3 and,E3-W3, forexample) are vertically separated by an amount where d is the ratio atthe operating frequency of the propagation velocity of feeder line .Sito the propaagtion velocity of free-space and is the free-spacewavelength. Furthermore, adjau cent elements in each oi the mutuallyperpendicular panels are separated by amount equal to ai. in thismanner, in-phase excitation of all elements in each panel is assured.

It is apparent that, while the vetrical separation between adjacentelements in each panel has been set forth as substantially ai, anyintegral multiple of this value may be used. Similarly, the verticalseparation between corresponding elements of the respective panels maybe any odd integral multiple of it may be desirable to choose suchvalues of terminal impedances or" thev radiating elements and suchcharacteristic impedance values for the various sections of the feederline as to eiect substantially equal power distribution between theradiating elements. rihere is .shown in litige1 nre 3, in schematicform, an approximate equiva lent circuit for an antenna comprising aseries of c radiating elements R1, R2 R11 mutually displaced along atransmission line by distances n: y, where :n and y are each equal to aquarter wavelength of the transmission line or any odd integral multiplethereof. For example, .7: may represent an electrical quarter wavelengthof the transmission line and y may represent an electricalthree-quarters wavelength of the line ah 3-) l which case R1 representsthe terminal` imped-s .cf Dlenient Re represents the terminal impedanceof element llt-fwd, etc. (Fig For equal power distribution between the nradiating elements, the follcwing condition has been round to obtain:

2 R R 1 Zccn n (m*1)2 on c (no where Rm represents the resistiveterminal im pedance of any one of the elements, Zum-o represents thecharacteristic impedance of the section of transmission line feeding thesame element, and m is any integer from 2 to n.

rihere is shown in Figure Il a graphical representation of powergain-vertical separation char acteristcs of typical turnstile antennasof differing number of bays. From the curves l-ll3, it is apparent thatincreased power gain is obtainable by increasing the number of baysemployed; furthermore, for any given number of bays, there is an optimumseparation between bays for which spacing maximum power gain isobtained. rlhe increased power gain at spacings greater than one-halfwavelength is due to the effect of the mutual impedances whereby theresistive component of terminal impedance of the individual radiatingelement is reduced, pern mitting larger current per unit power. As anincident advantage, it is found that the reactive components of themutual impedances, which must be compensated for by adjustment of theterminal impedances of the radiating elements,

are substantially less at optimum spacing than at the conventionalhalfwave spacing. Thus, an optimum spacing curve 44, connecting themaxima of the power gain characteristics en -63, may be drawn. It isthen apparent that an optimum power gain of about 3.4 is obtainable witha four-bay turnstile antenna having a spacing between adjacent elementsin each panel of about 0.78 Optimum spacing varies from about 0.68k fora two-bay antenna to about 0.84K for an eightbay antenna.

Referring again to the antenna of Figure 2, and recalling that optimumspacing for a fourbay antenna is 0.78K, adjacent elements in each panel(N3- S3 and Nfl-S4, for example) are vertically separated by about(178A, and the coaxial feeder line 3| is designed, in a manner to behereinafter more fully described, to have a propagation velocity equalto 0.78 oi that of free space. In this manner, optimum power gain isobtained while minimizing the required number of line ttings andeliminating the necessity for phasing loops.

Figure 5 shows a cross-sectional view of a ccu axial line suitable foruse as a feeder el in anv antenna such as that shown and described inconnection with Figure 2. The feeder line comprises an inner conductor50 coaxially supported within an outer conductor 5| by means of a number of dielectric beads or spacers 52. Such a beaded coaxial line may bedesigned for any propagation velocity ratio within a wide range asfollows:

For bead spacing s substantially less than a quarter-wavelength, thepropagation velocity is inversely proportional to the square root of theaverage dielectric constant. It has been determined that cylindricalbeads determine the propagation velocity of an air-dielectric coaxialline in accordance with the following equation:

a ruk-ride where a is the ratio of line to free-space propaga tionvelocities, 7c is the bead dielectric constant, d is the bead thickness,and s is the bead spacing. The ratio d/s is the fraction of thedielectric volume occupied by the beads, which fraction be used in anapproximate solution for a, when beads of non-cylindrical form are used.

Thus, if a velocity ratio a` of 0.75 is required, the ratio of beadthickness to spacing is d/s=0.156 for a ceramic bead having a dielectricconstant 7c of 6.

The transmission line surge impedance is re duced by the beads in thesame ratio as the propagation velocity. That is,

where Zo is the surge impedance of a line ccnstructed without beads andZn is the surge impedance of the beaded line. A larger conductor--diameter ratio must be used to obtain a given surge impedance in thepresence of insulating beads, the required ratio being:

60 comprises a dielectric bushing' 0| through which the radiatingelement E2 is connected to the feeder line. Element 52 corresponds toleg 2| of element 20 of Figure 1. For the uppermost radiating element(N4- S4 of Figure 2, for example) a fitting 63 such as that shown inFigure '7, which also comprises a dielectric bushing 64 through whichthe radiating element G5 is connected to the feeder line 3l, may beemployed.

While the antenna of Figure 2 has been shown comprising a single feederline, it is apparent that in some applications it may be desirable toemploy a pair of feeder lines rising from a common junction. In such anvembodiment, the feeder lines may be disposed about the outer surface ofthe supporting mast 30, as shown in Figure 8, and the radiating elementsconstituting each bay may be oriented in any of three ways as shown inFigures 8a, 8b, and 8c. If optimum spacing is employed between bays andthe necessity for transposition is eliminated by the use of a properlyloaded line, all bays would employ the same orientation, i. e. any oneof the orientations illustrated in Figures 8a, 8b, and 8c, depending onwhich is most convenient.

There are shown in. Figure 9 in simplified schematic form severaldiagrams representing the horizontal radiation patterns for an antennasuch as that shown in Figure 2 for different angles of elevation fromthe horizontal. In the horizontal plane including the center Iof theantennna array, the respective elements constituting a bay (N3-SLB andE3-W3 of Figure fer example) are equally distant from a remote receivingpoint (not shown). Therefore, the signal components from these elementshave the same quadrature relationship which they would possess ifelements N3-S3 and E3-W3 were coplanar and phased by means of a loopedquarter-Wave line. Such a radiation pattern (for the horizontaldirection, zero angle of elevation) is shown schematically in Figure 9a,and is substantially omnidirectional.

For a 90 angle of elevation (i. e., in the vertical direction) thehorizontal radiation pattern for a turnstile antenna such as that shownin Figure 2 is approximately of the form of figureeight with its axisrotated 45 from the axis of either radiating element. Such a radiationpattern is shown schematically in Figure 9b.

At angles of elevation intermediate 0 and 90, the horizontal pattern isintermediate the pattern shown in Figures 9a and 9b; for example, thereis shown in Figure 9c a schematic representation of the horizontalradiation pattern for an angle of elevation of 45.

In practice, the deviation of the radiation pattern from itssubstantially omnidirectional form as the angle of elevationis increasedis of little or no consequence, since normal radiation and normal gainare obtained in the horizontal direction.

In certain applications, it may be desirable to employ additionalradiating elements; such additional radiating elements may be added tothe antenna represented in Figure 2 in the manner illustratedschematically in Figure 10. In such an embodiment, the verticalseparation between adjacent elements is always and each element isadvanced 90 in azimuth from the preceding element. A single coaxialfeeder line has its inner conductor 80 connected to each of theradiating elements. The outer conductor 8| is connected to each simpledipole arm and to one end of each folded dipole arm and is grounded.

In lieu of mutually displacing the radiating elements constituting eachbay, they may be oriented in the same horizontal plane and fed byindividual feeders which are excited in phase quadrature. Such anembodiment is shown schematically in Figure 11, in which four hays ofradiating elements are shown. Adjacent elements in each panel (N4- S4and N3-S3, for example) are displaced in azimuth to provide the requiredtransposition. A pair of feeder lines 9| and 92 are employed; allelements in each panel are connected to the same feeder line, and the respective elements constituting each bay are connected to differentfeeder lines. Feeder lines 9| and 92 may be paralleled at the base ofthe antenna. A quarter-wave phasing loop 93 is connected in series withone of the lines (here shown in series with line 9|) in order to providequadrature excitation of the respective elements constituting each bay.

The use of a coaxial line having a propagation velocity which is relatedto the free-space propagation Velocity in the same ratio as is thephysical spacing between radiating elements to a free-space wave-lengthmay be also employed in antennas utilizing conventional radiatingelements, such as those of the folded dipole type. There is shown inschematic form in Figure 12 such an antenna, which is substantiallyidentical with the embodiment of Figure 2 with the exception that foldeddipole radiating elements are used, and balanced feeding is required. Asshown, the respective ends of each folded dipole are connected to one ofa pair of coaxial feeder lines |00 and IUI. Adjacent elements (NS-SS andN2-S2 for example) in each panel are separated by an amountsubstantially equal to the ratio of the propagation velocity of thefeeder line to that of free-space multiplied by a freespace wavelength.

While the invention has been described in connection with an antennaembodying a plurality of radiating elements, it is contemplated that, inView 0f the well-known reciprocal relaw tions existing betweentransmitting and receiving antenna elements, the radiating elementsdisclosed and claimed herein may be utilized either for the transmissionor reception of high frequency energy. Furthermore, although theinvention has been particularly described in connection with turnstileantennas, it is contemplated that the invention may also be applied tobroadside arrays incorporating only one panel of radiating elements.

While the invention has been shown and described in connection withcertain preferred embodiments, it is to be understood that numerousmodications and variations may be made, and it is contemplated in theappended claims to cover all such modifications and variations as fallwithin the true spirit and scope of the invention.

I claim:

1. An antenna including, in combination: a grounded conductive mast; acoaxial transmis sion line feeder disposed within said-mast; anunbalanced dipole radiating element comprising a folded dipole arm and asimple dipole arm collinear with and electrically connected to one legof said folded dipole arm; a connection from the inner conductor of saidfeeder to the unconnected leg of said folded dipole arm; and a aefiaasc9 connection from the junction `of said folded dipole arm and saidsimple dipole arm to said grounded mast and to the outer conductorA ofsaid feeder.v

2. An antenna comprising, in combination: a plurality of verticallyseparated radiating elements each of which comprises a folded -dipolearm and a simple dipole arm collinear with and electrically connected toone leg of said folded dipole arm; and a loaded transmission line feederinterconnecting said elements and having a propagation velocitymaterially less than that of free space; the ratio of the physicalseparation between adjacent elements to a free-space wavelength beingsubstantially equal to an integral multiple of the ratio of thepropagation Velocity-of said feeder line to the propagation velocity offree space.

3. An antenna for radiating high frequency energy into space, andincluding, in combination:

a grounded conductive mast; a plurality of un- 1balanced radiatingelements supported on said rnast in a pair of mutually perpendicularpanels; a coaxial feeder line disposed within said mast andinterconnecting said elements; the separation in each panel betweenadjacent elements being substantially an integral multiple of the 4. Aturnstile antenna comprising, in combinal tion: a plurality of spacedradiating elements disposed in each of a pair of vertical panels andeach comprising a folded dipole arm and a simple dipole arm collinearwith and electrically con nectcd to one leg of said folded dipole arm;and a feeder line interconnecting said elements, the ratio of thephysical separation between adjacent elements in each of said panels toa free-space wavelength being substantially equal to an integralmultiple of the ratio of the propagation Velocity of said feeder line tothe propagation velocity of free-space, and corresponding elements ofsaid panels being displaced with respect to each other by a distancesubstantially equal to an integral multiplied by a free-spacequarterwavelength.

5. A turnstile antenna comprising, in combination: a plurality of spacedradiating elements disposed in each of a pair of mutually perpendicularvertical panels and each element comprising a folded dipole arm and asingle dipole arm collinear with and electrically connected with one legof said folded dipole arm; and a feeder line interconnecting saidelements, the ratio of the physical separation between adjacent elementsin each of said panels to a free-space wavelength being substantiallyequal to an integral multiple of the ratio of the propagation velocityof said feeder line to the propagation velocity of free space, andcorresponding elements of said panels being displaced with respect toeach other by a distance substantially equal to an odd integral multipleof said propagation velocity ratio multiplied by a free-spacequarter-wavelength.

5. A turnstile antenna comprising, in combination: a plurality of spacedradiating elements supported on a conductive mast in each of a pair ofvertical panels and each comprising a folded dipole arm and a simpledipole arm collinear with l0 and electrically connected to one leg Vofsaid folded dipole arm; and a coaxial feeder line interconnecting saidelements, the separation between adjacent elements in each panel beingsubstantially Oak and the separation between corresponding elements ofsaid panels being substantially nauw? where c and n are integers, a isthe ratio of the propagation velocityv of said feeder line to thepropagation velocity of free-space, and A is a free-space wavelength.

'7. A. turnstile antenna comprising, in combination: a plurality ofspaced radiating elements supported on a conductive mast in each of apair of vertical panels and each comprising a folded dipole arm and asimple dipole arm collinear with and electrically connected to one legof said folded dipole arm; and a coaxial feeder line interconnectingsaid elements, the separation between adjacent elements in each panelbeing substantially A and the separation between corresponding elementsof said panels being substantially @wenig where c and n are integers, ais the ratio of the propagation velocity of said feeder line to thepropagation velocity of free-space, and A is a freespace wavelength; andthe terminal impedances of said elements and the characteristicimpedances of the feeder line portions between adjacent elements beingchosen substantially in accordance with the formula l Zagen-1) (iRtm-Rmwhere Rm is the resistive terminal impedance of any one of saidelements, Zoon-1) is the characteristic impedance of the section of saidfeeder line feeding the same element, and m is any integer from 2 to n.

8. A turnstile antenna comprising, in combination: a pair of crossedpanels of radiating elements each of which comprises a directly excitedfolded dipole arm and a parasitically excited simple dipole armcollinear with and electrically connected to one leg of said foldeddipole arm; a first feeder line interconnecting all of the elements ofone of said panels; a second feeder line interconnecting all of theelements of the other of said panels; and means for exciting said feederlines in phase quadrature.

9. A turnstile antenna comprising, in combination: a pair of crossedpanels of radiating elements each of which comprises a folded dipole armand a simple dipole arm collinear with and electrically connected to oneleg of said folded dipole arm; a first loaded transmission line feederinterconnecting all of the elements of one of said panels and having apropagation velocity materially less than that of free space; a secondloaded transmission line feeder interconnecting all of the elements ofthe other of said panels and having a propagation velocity substantiallyequal to that of said first feeder; and means for eX- citing said feederlines in phase quadrature, the ratio of physical separation betweenadjacent elements in each of said panels to a free-space armsubstantially =collinear. With :and electrically connectedt toone leg of-,said ,folded dipolearm:

and means, including a transmission line feeder Y 'I0 connected to theother :leg of said folded dipole arm, for directly exciting said foldeddipole arm only. i

An unbalanced-dipoleradiating element comprising: a-.foldeddipole arm;.a simpledipole arm substantially collinearwithand electrically connectedto -one leg of `said..fold`ed..dipoleA afm; saidsimple. dipole. armbeing offsubs'tantiallyfthe same. length`v` as saidV folded-dipole.-arrln; land meaims,l including-a transmission line feeder con--lnectedtoathe otherleg offsaid'folded dipole arm,

for directly exciting saidtolded dipole 'arm only. :512. A ,halfswaveunbalanced dipole.:.radiating element comprising: a 'quarter-wavelengthfolded 12 nipote rm; dayterjmugtn 'simple 'dipole a'r'xn`sibst'anti"ally collinear with and electrically cone'ctd t ieg "of said'romeu dip'oiefarma andmpeans, including artransmission line 'feeder'connected 't 'the ,other 'l'gfof said folded vdipole airn, f'r directly'c'iting 'said folded Vdipole "arm only. I A

NATHAN W.

'Rfns Cited in fue nie of vthis :patent UNTED STATES PATENTS .Nhieflaite. 2,234,744 .Thomas Mar. 1l, 11,9;41 .2,258,953 Higgins L; Oct.1,4,` 1 941 ,2,338,564 4Aram zjJa/n. 4, 19M 2,521,550 smith sept. 5,1950 r b. FOREIGN PATENTS Number.. .c'nffy, me 20 Y l581,567 GreatBritain oct. 17. 1946

